Influences of Mild Oxidation Treatment on the Structure and Electrochemical Behavior of Spherical Graphite

doi:10.3724/SP.J.1077.2012.00151

Abstract

Abstract:

The effects of mild oxidation treatment on the crystal structure, morphology and electrochemical behavior of spherical graphite were investigated. The structure and morphology of the samples were characterized by XRD, Raman spectra and SEM analysis, respectively. The electrochemical behavior of the samples was studied using galvanostatic charge/discharge test, powder cavity microelectrode technique and slow scan rate cyclic voltammograms. The results indicate that structural defects in graphite particles and disordered degree of near surface region of graphite increase after modification, while the average in-plane crystallite domain size L_aand content of rhombohedral phase decrease. The graphite particles present irregular flake shape and some graphene sheets show flexual and sculptural margin. Electrochemical measures show that reversible capacity of modified graphite increases from 345.5 mAh/g to 381.4 mAh/g, and cycling performance is improved. During deintercalation process of the modified graphite, stage transformation from stage 1 Li-GICs (lithium-graphite intercalation compounds) to stage 2 Li-GICs begins to happen at lower voltage, compared with that of the raw graphite.

Key words: lithium-ion batteries, anode material, spherical graphite, oxidation treatment, electrochemical behavior

CLC Number:

TM912

JIAN Zhi-Min, LIU Hong-Bo, SHI Lei, HE Yue-De, XIAO Hai-He, KUANG Jia-Cai. Influences of Mild Oxidation Treatment on the Structure and Electrochemical Behavior of Spherical Graphite[J]. Journal of Inorganic Materials, 2012, 27(2): 151-156.

Figures/Tables 8

Fig. 1 XRD patterns of spherical graphite before (SG) and after (MSGO) mild oxidation treatment

Table 1 The structural properties of spherical graphite before (SG) and after (MSGO) mild oxidation treatment

Sample	d₀₀₂/nm	Content of 3R phase/wt%	R value	L_a/nm	D₅₀/μm
SG	0.33553	21.3	0.15	30.35	28.2
MSGO	0.33554	9.9	0.21	20.85	27.6

Fig. 2 Raman spectra of spherical graphite before (SG) and after (MSGO) mild oxidation treatment

Fig. 3 SEM images of spherical graphite before (a) and (b) and after (c) and (d) mild oxidation treatment

Fig. 4 DFT pore size distributions of spherical graphite anode before (SG) and after (MSGO) mild oxidation treatment

Fig. 5 First three charge-discharge curves of spherical graphite anode before (SG) and after (MSGO) mild oxidation treatment

Fig. 6 Repeated CVs profile of spherical graphite anode before (a) and after (b) mild oxidation treatment

Fig. 7 Slow scan rate cyclic voltammograms of spherical graphite anode before (SG) and after (MSGO)mild oxidation treatment

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